Cancer is a leading cause of death in developed countries. Despite continuing advances in diagnosis and treatment regimens, most existing treatment methods have undesirable side effects and limited efficacy. Treatment of cancer is complicated by the variety of mechanisms involved in the formation and metastasis of tumors. Many of them are still not well understood. Chemotherapy is a major option for the first-line treatment in cancers such as leukemia and second-line treatment for cancers such as refractory solid tumor. Most current anticancer drugs are small molecule chemicals.